Air-fuel delivery systems can be broadly classified into two groups, fuel injection and carburetion.
In the case of fuel injection, there are two basic types of systems, one which combines the pump and injector into a single unit and the other which has an independent pump which feeds a plurality of electronically or otherwise operated injectors.
Although the above described systems are able to accurately inject fuel with respect to time and quantity, they suffer from drawbacks including complex construction and high cost.
In the case of carburetion, modern carburetors, due to the ever-increasing demand for more accurate control of the air-fuel mixture for the facilitation of reduction of noxious compounds emitted from internal combustion engines and the simultaneous maximization of fuel economy and power output, have become exceedingly complex with an accompanying loss of reliability.
Thus, in order to solve the above-mentioned drawbacks, a fuel atomizing apparatus for an air-fuel delivery system which employs electrostatic attraction and repulsion, or electrostatic spray phenomenon as it will be referred to hereinafter, has been proposed by the present applicant in the U.S. patent application Ser. No. 778,994 abandoned filed on Mar. 18th, 1977.
In the above-mentioned apparatus a plurality of fine tubes which are fluidly connected to a source of fuel are arranged to open into an intake passage of, for example, an internal combustion engine. An electrode is arranged adjacent the openings of the fine tubes so that on applying a high voltage across the fine tubes and the electrode, the fuel having had a charge imparted thereto is simultaneously attracted and repulsed to and from the electrode and fine tubes respectively. The fuel is thus jetted into the intake passage to mix with and form a mist of fuel in the air passing therethrough.
The rate of discharge from the fine tubes is in the above-mentioned apparatus responsive to the voltage applied. To supply a given volume of fuel per unit time, either a small number of large diameter tubes or a rather large number of small diameter tubes are required. However, in the case of a small number of large diameter tubes, it has been found that the change in the fuel flow rate induced by a given change in the voltage applied across the electrodes is in fact undesirably small, and if the diameter is overly large there is no spray phenomenon produced. Further, in the case of a large number of small diameter tubes, although a desirable spray phenomenon is produced, the device tends to become overly complex due to the aforementioned large number of tubes and if the internal diameter of the tubes becomes too small, undesirable fluctuations in the flow rate therethrough occur. Furthermore, control efficiency drops off sharply at low voltages and the arrangement requires a greater range of voltage applied thereto, to achieve a suitable fuel flow range, as compared with the case of a small number of large tubes.
Hence, in the present invention, by using a small number of relatively large diameter tubes which are stepwisely closable by a piston which moves in response to the amount of intake air, a range of voltage which is smaller than that used in the case of many small diameter tubes can be employed.